Academic Commons Search Resultshttp://academiccommons.columbia.edu/catalog.rss?f%5Bauthor_facet%5D%5B%5D=Schimmelpfennig%2C+Irene+Lois&f%5Bauthor_facet%5D%5B%5D=Schaefer%2C+Joerg+M.&f%5Bpub_date_facet%5D%5B%5D=2012&q=&rows=500&sort=record_creation_date+desc
Academic Commons Search Resultsen-usCalibration of the in situ cosmogenic 14C production rate in New Zealand's Southern Alpshttp://academiccommons.columbia.edu/catalog/ac:152888
Schimmelpfennig, Irene Lois; Schaefer, Joerg M.; Goehring, Brent M.; Lifton, Nathaniel; Putnam, Aaron Ervin; Barrell, David J. A.http://hdl.handle.net/10022/AC:P:14785Thu, 27 Sep 2012 00:00:00 +0000In situ cosmogenic 14C (in situ 14C) analysis from quartz-bearing rocks is a novel isotopic tool useful for quantifying recent surface exposure histories (up to ∼25 ka). It is particularly powerful when combined with longer-lived cosmogenic isotopes such as 10Be. Recent advances in the extraction of in situ 14C from quartz now permit the routine application of this method. However, only a few experiments to calibrate the production rate of in situ 14C in quartz have been published to date. Here, we present a new in situ 14C production rate estimate derived from a well-dated debris flow deposit in the Southern Alps, New Zealand, previously used to calibrate 10Be production rates. For example, based on a geomagnetic implementation of the Lal/Stone scaling scheme we derive a spallogenic production rate of 11.4 ± 0.9 atoms 14C (g quartz)−1 a−1 and a 14C/10Be spallogenic production rate ratio of 3.0 ± 0.2. The results are comparable with production rates from previous calibrations in the northern hemisphere.Geologyils2113, jms2003, ap2495Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticlesHolocene glacier culminations in the Western Alps and their hemispheric relevancehttp://academiccommons.columbia.edu/catalog/ac:152891
Schimmelpfennig, Irene Lois; Schaefer, Joerg M.; Akcar, Naki; Ivy-Ochs, Susan; Finkel, Robert C.; Schlüchter, Christianhttp://hdl.handle.net/10022/AC:P:14786Thu, 27 Sep 2012 00:00:00 +0000The natural variability of Holocene climate defines the baseline to assess ongoing climate change. Greenland ice-core records indicate warming superimposed by abrupt climate oscillations in the early Holocene, followed by a general cooling trend throughout the middle and late Holocene that culminated during the Little Ice Age (LIA). Tropical precipitation changes correlate with these patterns throughout the Holocene. Here we use mountain glaciers in the European Alps to reconstruct the regional Holocene climate evolution and to test for a link between mid-latitude, North Atlantic, and tropical climate. Our precise 10Be chronology from Tsidjiore Nouve Glacier, western Swiss Alps, indicates a glacier culmination during the earliest Holocene ∼11.4 k.y. ago, likely related to the Preboreal Oscillation. Based on our data, no Holocene glacier advance of similar amplitude occurred until ∼3.8 k.y. ago, when the glacier reached LIA limits. The 10Be ages between 500 and 170 yr correspond to the LIA, while the youngest 10Be ages overlap with the historically recorded post-LIA glacier positions. Integrating our data with existing records, we propose a hemispheric climate link between the Alps, North Atlantic temperature, and tropical precipitation patterns for the Holocene, supporting the concept of a pervasive climate driver. These findings from northern mid-latitudes are consistent with the hypothesis formulated for the tropics that the Earth’s thermal equator, responding to North Atlantic temperature changes, might have migrated southward throughout the Holocene, reaching the southern turning point toward the end of the LIA.Geology, Climate changeils2113, jms2003Lamont-Doherty Earth Observatory, Earth and Environmental SciencesArticles